The present invention relates to a medical instrument, which is designed, to be inserted into a patient's body through the instrument-guiding channel of an endoscope, already inserted into the patient's body, for cutting living tissues continuously and collecting a plurality of living-tissue samples.
Known as a medical instrument for sampling living tissues is the one disclosed in International Publication WO 95/08291. FIG. 24A is a diagram showing the main section of the instrument (a) disclosed in the publication. FIG. 24B is a diagram showing the medical instrument (a) in use. The medical instrument (a) comprises an outer sheath (b) and an inner sheath (c). The outer sheath (b) is flexible and can be inserted into a forceps channel of an endoscope. The inner sheath (c) is inserted in the outer sheath (b).
The inner sheath (c) has an opened distal end (d). The outer sheath (b) has a cutting means (e) at its distal end. The cutting means (e) is designed to cut living tissues (p). The cutting means (e) is biased in a direction, closing the distal end of the outer sheath (b). The cutting means (e) can cut living tissues (p) when it is moved, closing the opened distal end (d) of the inner sheath (c).
A retractor (f) is provided in the inner sheath (c) and can be moved in the axial direction of the inner sheath (c). The pieces (p1), (p2), (p3) and (p4) of the living tissue, cut by the cutting means (e), are sequentially guided into the inner sheath (c), from the opened distal end of the inner sheath (c). The retractor (f) pushes these pieces from the opened distal end of the inner sheath (c).
How the medical instrument (a) is used will be explained. First, the instrument (a) is inserted into a forceps channel of an endoscope, which has already been inserted to a patient's body. The instrument (a) is guided into the patient's body until its distal end reaches the target tissue (p) present in the patient's body. Then, as shown in FIG. 24B, the inner sheath (c) is thrust from the distal end of the outer sheath (b). The tissue (p) is thereby caught in the opened distal end (d) of the inner sheath (c).
The inner sheath (c) is then moved back in its axial direction and pulled into the outer sheath (b). As the inner sheath (c) is thus moved, the cutting means (e) cuts the tissue (p) because it is biased and closing the distal end of the outer sheath (b). The pieces (p1), (p2), (p3) and (p4) of the tissue (p), thus cut, are sampled into the tissue-storing space (g) provided in the inner sheath (c).
The tissue-sampling sequence described above is repeated several times. The pieces (p1), (p2), (p3) and (p4) sampled into the tissue-storing space (g) in the first sampling sequence are pushed toward the proximal end of the medical instrument (a) as other pieces of tissue are sampled. When the last tissue-sampling sequence completes, the instrument (a) is pulled out of the endoscope. The retractor (f) is pushed forward from the opened distal end (d) of the inner sheath (c). The pieces (p1), (p2), (p3), (p4) and so on, all sampled, are thereby collected.
European Patent EP 0 065 054 discloses a medical instrument (k), which is shown in FIGS. 24C and 24D. The instrument (k) comprises a hollow cylinder (h), and a cutting means (j). The cutting means (j) comprises a pair of arms (i) provided partly in the cylinder (h). The each arm (i) is formed by bending the distal ends of the members at right angles. When the arms (i) are pulled in the cylinder (h), and toward the proximal end thereof, the cutting means (j) cuts a living tissue (p).
When the medical instrument disclosed in International Publication W0095/08291 is used, the distal end of the inner sheath (c) must pierce the target living tissue (p), from the surface of the tissue (p). It is difficult, however, for the inner sheath (c) to plunge deep into the tissue (p) to sample a piece at a relatively deep position in the tissue (p). For doctors, too, it is hard to thrust the sheath (c) so deep into the tissue (p).
The opened distal end of the inner sheath (c) is sharpened enough to pierce the living tissue (p). Should the distal end of the inner sheath (c) touch any tissue other than the target tissue (p), it would damage the tissue. Much care should therefore be taken to manipulate the medical instrument (a).
With the medical instrument disclosed in European Patent EP 0 065 054 it is easy to sample a piece of the living tissue (p) if the cylinder (h) contacts the tissue (p), with its axis extending at right angles to the tissue (p). If the cylinder (h) is positioned with its axis extending at right angles or inclined to the living tissue (p), however, no part of the tissue (p) can be sampled. This is because no teeth are provided on the circumferential surface of the cylinder (h).